@article{huang_thomas_2024, title={Energy-resolved spin correlation measurements: Decoding transverse spin dynamics in weakly interacting Fermi gases}, url={https://doi.org/10.1103/PhysRevA.109.L041301}, DOI={10.1103/PhysRevA.109.L041301}, abstractNote={The authors measure transverse spin correlations in energy space to uncover hidden spin dynamics in a weakly interacting Fermi gas. The correlation functions reveal the microscopic structure of a demagnetizing or magnetizing synthetic spin lattice, which models a collective Heisenberg Hamiltonian, and provide new observables for studies of transitions between dynamical phases.}, journal={Physical Review A}, author={Huang, J. and Thomas, J. E.}, year={2024}, month={Apr} }
 @article{huang_royse_arakelyan_thomas_2023, title={Verifying a quasiclassical spin model of perturbed quantum rewinding in a Fermi gas}, volume={108}, ISSN={["2469-9934"]}, url={https://doi.org/10.1103/PhysRevA.108.L041304}, DOI={10.1103/PhysRevA.108.L041304}, abstractNote={We systematically test a quasi-classical spin model of a large spin-lattice in energy space, with a tunable, reversible Hamiltonian and effective long-range interactions. The system is simulated by a weakly interacting Fermi gas undergoing perturbed quantum rewinding using radio-frequency(RF) pulses. The model reported here is found to be in a quantitative agreement with measurements of the ensemble-averaged energy-resolved spin density. This work elucidates the effects of RF detunings on the system and measurements, pointing the way to new correlation measurement methods.}, number={4}, journal={PHYSICAL REVIEW A}, author={Huang, J. and Royse, Camen A. and Arakelyan, I. and Thomas, J. E.}, year={2023}, month={Oct} }
 @article{wang_li_arakelyan_thomas_2022, title={Hydrodynamic Relaxation in a Strongly Interacting Fermi Gas}, volume={128}, ISSN={["1079-7114"]}, url={https://doi.org/10.1103/PhysRevLett.128.090402}, DOI={10.1103/PhysRevLett.128.090402}, abstractNote={We measure the free decay of a spatially periodic density profile in a normal fluid strongly interacting Fermi gas, which is confined in a box potential. This spatial profile is initially created in thermal equilibrium by a perturbing potential. After the perturbation is abruptly extinguished, the dominant spatial Fourier component exhibits an exponentially decaying (thermally diffusive) mode and a decaying oscillatory (first sound) mode, enabling independent measurement of the thermal conductivity and the shear viscosity directly from the time-dependent evolution.}, number={9}, journal={PHYSICAL REVIEW LETTERS}, author={Wang, Xin and Li, Xiang and Arakelyan, Ilya and Thomas, J. E.}, year={2022}, month={Mar} }
 @article{pegahan_arakelyan_thomas_2021, title={Energy-Resolved Information Scrambling in Energy-Space Lattices}, volume={126}, ISSN={["1079-7114"]}, url={https://doi.org/10.1103/PhysRevLett.126.070601}, DOI={10.1103/PhysRevLett.126.070601}, abstractNote={Weakly interacting Fermi gases simulate spin lattices in energy space, offering a rich platform for investigating information spreading and spin coherence in a large many-body quantum system. We show that the collective spin vector can be determined as a function of energy from the measured spin density, enabling general energy-space resolved protocols. We measure an out-of-time-order correlation function in this system and observe the energy dependence of the many-body coherence.}, number={7}, journal={PHYSICAL REVIEW LETTERS}, author={Pegahan, S. and Arakelyan, I and Thomas, J. E.}, year={2021}, month={Feb} }
 @book{thomas_2020, title={Fermi Gases in Bichromatic Superlattices}, url={https://doi.org/10.2172/1573239}, DOI={10.2172/1573239}, abstractNote={The purpose of the program is the broad study of designer materials made of ultra-cold atoms and light, which provides new paradigms for emulating exotic layered systems. Bichromatic superlattices enable control and study of both dimensionality and dispersion in layered, strongly correlated Fermi gases, to model high-temperature superfluidity/superconductivity. Most layered materials are quasi-two-dimensional, neither two-dimensional, like a sheet, nor three-dimensional, like a gas, but somewhere in between. In quasi-2D layers with an unequal number of spin-up and spin-down electrons, particularly strong attraction between pairs of electrons with opposite spins is predicted to achieve the highest possible superconducting transition temperatures. To understand these materials, we emulate them with a layered, ultra-cold Fermi gas of 6Li atoms, magnetically tuned near a collisional (Feshbach) resonance, where precise control of the attraction, spin-composition, dimensionality and dispersion provides new tests of theory. The primary goals are of the program are: (1) Elucidation of the effects of dimensionality and confining potential shape on the enhancement of high-temperature superfluidity in a layered, strongly correlated Fermi gases; (2) Control of dispersion and the study of tunable Dirac points in one dimension.}, author={Thomas, John}, year={2020}, month={Feb} }
 @article{arunkumar_jagannathan_thomas_2019, title={Designer Spatial Control of Interactions in Ultracold Gases}, volume={122}, ISSN={["1079-7114"]}, DOI={10.1103/PhysRevLett.122.040405}, abstractNote={Designer optical control of interactions in ultracold atomic gases has wide applications, from creating new quantum phases to modeling the physics of black holes. We demonstrate wide tunability and spatial control of interactions in a two-component cloud of ^{6}Li fermions, using electromagnetically induced transparency. With two control fields detuned ≃1.5  THz from atomic resonance, megahertz changes in the frequency of one optical beam tune the measured scattering length over the full range achieved by magnetic control, with negligible (10^{-6}) effect on the net optical confining potential. A 1D "sandwich" of resonantly and weakly interacting regions is imprinted on the trapped cloud and broadly manipulated with sub-MHz frequency changes. All of the data are in excellent agreement with our continuum-dressed state theoretical model of optical control, which includes both the spatial and momentum dependence of the scattering amplitude.}, number={4}, journal={PHYSICAL REVIEW LETTERS}, author={Arunkumar, N. and Jagannathan, A. and Thomas, J. E.}, year={2019}, month={Feb} }
 @article{baird_wang_roof_thomas_2019, title={Measuring the Hydrodynamic Linear Response of a Unitary Fermi Gas}, volume={123}, ISSN={["1079-7114"]}, url={https://doi.org/10.1103/PhysRevLett.123.160402}, DOI={10.1103/PhysRevLett.123.160402}, abstractNote={We directly observe the hydrodynamic linear response of a unitary Fermi gas confined in a box potential and subject to a spatially periodic optical potential that is translated into the cloud at speeds ranging from subsonic to supersonic. We show that the time-dependent change of the density profile is sensitive to the thermal conductivity, which controls the relaxation rate of the temperature gradients and hence the responses arising from adiabatic and isothermal compression.}, number={16}, journal={PHYSICAL REVIEW LETTERS}, publisher={American Physical Society (APS)}, author={Baird, Lorin and Wang, Xin and Roof, Stetson and Thomas, J. E.}, year={2019}, month={Oct} }
 @article{pegahan_kangara_arakelyan_thomas_2019, title={Spin-energy correlation in degenerate weakly interacting Fermi gases}, volume={99}, ISSN={["2469-9934"]}, DOI={10.1103/PhysRevA.99.063620}, abstractNote={Weakly interacting Fermi gases exhibit rich collective dynamics in spin-dependent potentials, arising from correlations between spin degrees of freedom and conserved single atom energies, offering broad prospects for simulating many-body quantum systems by engineering energy-space "lattices," with controlled energy landscapes and site to site interactions. Using quantum degenerate clouds of $^6$Li, confined in a spin-dependent harmonic potential, we measure complex, time-dependent spin-density profiles, varying on length scales much smaller than the cloud size. We show that a one-dimensional mean field model, without additional simplifying approximations, quantitatively predicts the observed fine structure. We measure the magnetic fields where the scattering lengths vanish for three different hyperfine state mixtures to provide new constraints on the collisional (Feshbach) resonance parameters.}, number={6}, journal={PHYSICAL REVIEW A}, author={Pegahan, S. and Kangara, J. and Arakelyan, I and Thomas, J. E.}, year={2019}, month={Jun} }
 @article{kangara_cheng_pegahan_arakelyan_thomas_2018, title={Atom Pairing in Optical Superlattices}, volume={120}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.120.083203}, abstractNote={We study the pairing of fermions in a one-dimensional lattice of tunable double-well potentials using radio-frequency spectroscopy. The spectra reveal the coexistence of two types of atom pairs with different symmetries. Our measurements are in excellent quantitative agreement with a theoretical model, obtained by extending the Green's function method of Orso et al. [Phys. Rev. Lett. 95, 060402 (2005)PRLTAO0031-900710.1103/PhysRevLett.95.060402] to a bichromatic 1D lattice with nonzero harmonic radial confinement. The predicted spectra comprise hundreds of discrete transitions, with symmetry-dependent initial state populations and transition strengths. Our work provides an understanding of the elementary pairing states in a superlattice, paving the way for new studies of strongly interacting many-body systems.}, number={8}, journal={PHYSICAL REVIEW LETTERS}, author={Kangara, J. and Cheng, Chingyun and Pegahan, S. and Arakelyan, I. and Thomas, J. E.}, year={2018}, month={Feb} }
 @article{arunkumar_jagannathan_thomas_2018, title={Probing Energy-Dependent Feshbach Resonances by Optical Control}, volume={121}, DOI={10.1103/PhysRevLett.121.16344}, number={16}, journal={PHYSICAL REVIEW LETTERS}, author={Arunkumar, N. and Jagannathan, A. and Thomas, John}, year={2018} }
 @article{cheng_kangara_arakelyan_thomas_2016, title={Fermi gases in the two-dimensional to quasi-two-dimensional crossover}, volume={94}, ISSN={["2469-9934"]}, DOI={10.1103/physreva.94.031606}, abstractNote={We tune the dimensionality of pancake-shaped strongly-interacting Li Fermi gas clouds from twodimensional (2D) to quasi-2D, by controlling the ratio of the radial Fermi energy EF to the harmonic oscillator energy hνz in the tightly confined direction. In the 2D regime, where EF << hνz, the measured radio frequency resonance spectra are in agreement with 2D-BCS theory. In the quasi-2D regime, where EF ≃ hνz, the measured spectra deviate significantly from 2D-BCS theory. For both regimes, the measured cloud radii disagree with 2D-BCS mean field theory, but agree approximately with predictions using a free energy derived from the Bethe-Goldstone equation.}, number={3}, journal={PHYSICAL REVIEW A}, author={Cheng, Chingyun and Kangara, J. and Arakelyan, I. and Thomas, J. E.}, year={2016}, month={Sep} }
 @article{jagannathan_arunkumar_joseph_thomas_2016, title={Optical Control of Magnetic Feshbach Resonances by Closed-Channel Electromagnetically Induced Transparency}, volume={116}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.116.075301}, abstractNote={We control magnetic Feshbach resonances in an optically trapped mixture of the two lowest hyperfine states of a ^{6}Li Fermi gas, using two optical fields to create a dark state in the closed molecular channel. In the experiments, the narrow Feshbach resonance is tuned by up to 3 G. For the broad resonance, the spontaneous lifetime is increased to 0.4 s at the dark-state resonance, compared to 0.5 ms for single-field tuning. We present a new model of light-induced loss spectra, employing continuum-dressed basis states, which agrees in shape and magnitude with loss measurements for both broad and narrow resonances. Using this model, we predict the trade-off between tunability and loss for the broad resonance in ^{6}Li, showing that our two-field method substantially reduces the two-body loss rate compared to single-field methods for the same tuning range.}, number={7}, journal={PHYSICAL REVIEW LETTERS}, author={Jagannathan, A. and Arunkumar, N. and Joseph, J. A. and Thomas, J. E.}, year={2016}, month={Feb} }
 @article{joseph_elliott_thomas_2015, title={Shear Viscosity of a Unitary Fermi Gas Near the Superfluid Phase Transition}, volume={115}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.115.020401}, abstractNote={We measure the shear viscosity for a resonantly interacting Fermi gas as a function of temperature from nearly the ground state through the superfluid phase transition into the high temperature regime. Further, we demonstrate an iterative method to estimate the local shear viscosity coefficient α(S)(θ) versus reduced temperature θ from the cloud-averaged measurements ⟨α(S)⟩, and compare α(S) to several microscopic theories. We find that α(S) reveals features that were previously hidden in ⟨α(S)⟩.}, number={2}, journal={PHYSICAL REVIEW LETTERS}, author={Joseph, J. A. and Elliott, E. and Thomas, J. E.}, year={2015}, month={Jul} }
 @article{ong_cheng_arakelyan_thomas_2015, title={Spin-Imbalanced Quasi-Two-Dimensional Fermi Gases}, volume={114}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.114.110403}, abstractNote={We measure the density profiles for a Fermi gas of (6)Li containing N(1) spin-up atoms and N(2) spin-down atoms, confined in a quasi-two-dimensional geometry. The spatial profiles are measured as a function of spin imbalance N(2)/N(1) and interaction strength, which is controlled by means of a collisional (Feshbach) resonance. The measured cloud radii and central densities are in disagreement with mean-field Bardeen-Cooper-Schrieffer theory for a true two-dimensional system. We find that the data for normal-fluid mixtures are reasonably well fit by a simple two-dimensional polaron model of the free energy. Not predicted by the model is a phase transition to a spin-balanced central core, which is observed above a critical value of N(2)/N(1). Our observations provide important benchmarks for predictions of the phase structure of quasi-two-dimensional Fermi gases.}, number={11}, journal={PHYSICAL REVIEW LETTERS}, author={Ong, W. and Cheng, Chingyun and Arakelyan, I. and Thomas, J. E.}, year={2015}, month={Mar} }
 @article{elliott_joseph_thomas_2014, title={Anomalous Minimum in the Shear Viscosity of a Fermi Gas}, volume={113}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.113.020406}, abstractNote={We measure the static shear viscosity η in a two-component Fermi gas near a broad collisional (Feshbach) resonance, as a function of interaction strength and energy. We find that η has both a quadratic and a linear dependence on the interaction strength 1/(k(FI)a), where a is the s-wave scattering length and k(FI) is the Fermi wave vector for an ideal gas at the trap center. For energies above the superfluid transition, the minimum in η as a function of interaction strength is significantly shifted toward the BEC side of resonance, to 1/(k(FI)a)≃0.25.}, number={2}, journal={PHYSICAL REVIEW LETTERS}, author={Elliott, E. and Joseph, J. A. and Thomas, J. E.}, year={2014}, month={Jul} }
 @article{elliott_joseph_thomas_2014, title={Observation of Conformal Symmetry Breaking and Scale Invariance in Expanding Fermi Gases}, volume={112}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.112.040405}, abstractNote={We precisely test scale invariance and examine local thermal equilibrium in the hydrodynamic expansion of a Fermi gas of atoms as a function of interaction strength. After release from an anisotropic optical trap, we observe that a resonantly interacting gas obeys scale-invariant hydrodynamics, where the mean square cloud size = expands ballistically (like a noninteracting gas) and the energy-averaged bulk viscosity is consistent with zero, 0.00(0.04)ℏn, with n the density. In contrast, the aspect ratios of the cloud exhibit anisotropic "elliptic" flow with an energy-dependent shear viscosity. Tuning away from resonance, we observe conformal symmetry breaking, where deviates from ballistic flow.}, number={4}, journal={PHYSICAL REVIEW LETTERS}, author={Elliott, E. and Joseph, J. A. and Thomas, J. E.}, year={2014}, month={Jan} }
 @article{wu_thomas_2012, title={Optical Control of Feshbach Resonances in Fermi Gases Using Molecular Dark States}, volume={108}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.108.010401}, abstractNote={We propose a general method for optical control of magnetic Feshbach resonances in ultracold atomic gases with more than one molecular state in an energetically closed channel. Using two optical frequencies to couple two states in the closed channel, inelastic loss arising from spontaneous emission is greatly suppressed by destructive quantum interference at the two-photon resonance, i.e., dark-state formation, while the scattering length is widely tunable by varying the frequencies and/or intensities of the optical fields. This technique is of particular interest for a two-component atomic Fermi gas, which is stable near a Feshbach resonance.}, number={1}, journal={PHYSICAL REVIEW LETTERS}, author={Wu, Haibin and Thomas, J. E.}, year={2012}, month={Jan} }
 @article{wu_thomas_2012, title={Optical control of the scattering length and effective range for magnetically tunable Feshbach resonances in ultracold gases}, volume={86}, ISSN={["1094-1622"]}, DOI={10.1103/physreva.86.063625}, abstractNote={We describe two-field optical techniques to control interactions in Feshbach resonances for two-body scattering in ultra-cold gases. These techniques create a molecular dark state in the closed channel of a magnetically tunable Feshbach resonance, greatly suppressing optical scattering compared to single optical field methods. The dark-state method enables control of the effective range, by creating narrow features that modify the energy dependence of the scattering phase shift, as well as control of the elastic and inelastic parts of the zero-energy s-wave scattering amplitude. We determine the scattering length and the effective range from an effective range expansion, by calculating the momentum-dependent scattering phase shift from the two-body scattering state.}, number={6}, journal={PHYSICAL REVIEW A}, author={Wu, Haibin and Thomas, J. E.}, year={2012}, month={Dec} }
 @article{zhang_ong_arakelyan_thomas_2012, title={Polaron-to-Polaron Transitions in the Radio-Frequency Spectrum of a Quasi-Two-Dimensional Fermi Gas}, volume={108}, ISSN={["0031-9007"]}, DOI={10.1103/physrevlett.108.235302}, abstractNote={We measure radio-frequency spectra for a two-component mixture of a 6Li atomic Fermi gas in a quasi-two-dimensional regime with the Fermi energy comparable to the energy level spacing in the tightly confining potential. Near the Feshbach resonance, we find that the observed resonances do not correspond to transitions between confinement-induced dimers. The spectral shifts can be fit by assuming transitions between noninteracting polaron states in two dimensions.}, number={23}, journal={PHYSICAL REVIEW LETTERS}, author={Zhang, Y. and Ong, W. and Arakelyan, I. and Thomas, J. E.}, year={2012}, month={Jun} }
 @article{thomas_2011, title={Spin drag in a perfect fluid}, volume={472}, ISSN={0028-0836 1476-4687}, url={http://dx.doi.org/10.1038/472172a}, DOI={10.1038/472172a}, number={7342}, journal={Nature}, publisher={Springer Science and Business Media LLC}, author={Thomas, John E.}, year={2011}, month={Apr}, pages={172–173} }
 @article{thomas_2010, title={The nearly perfect Fermi gas}, volume={63}, ISSN={0031-9228 1945-0699}, url={http://dx.doi.org/10.1063/1.3431329}, DOI={10.1063/1.3431329}, abstractNote={To probe strongly interacting, ultracold fermionic atoms, experimenters view the size and oscillations of a gas cloud when it is trapped and the rotation of the cloud when it is released.}, number={5}, journal={Physics Today}, publisher={AIP Publishing}, author={Thomas, John E.}, year={2010}, month={May}, pages={34–37} }
 @article{cao_elliott_joseph_wu_petricka_schafer_thomas_2010, title={Universal Quantum Viscosity in a Unitary Fermi Gas}, volume={331}, ISSN={0036-8075 1095-9203}, url={http://dx.doi.org/10.1126/science.1195219}, DOI={10.1126/science.1195219}, abstractNote={Viscosity studies of an ultracold gas of6Li atoms in two temperature regimes enable comparison with a string theory limit.}, number={6013}, journal={Science}, publisher={American Association for the Advancement of Science (AAAS)}, author={Cao, C. and Elliott, E. and Joseph, J. and Wu, H. and Petricka, J. and Schafer, T. and Thomas, J. E.}, year={2010}, month={Dec}, pages={58–61} }
 @article{thomas_2009, title={Is an Ultra-Cold Strongly Interacting Fermi Gas a Perfect Fluid?}, volume={830}, ISSN={0375-9474}, url={http://dx.doi.org/10.1016/j.nuclphysa.2009.09.055}, DOI={10.1016/j.nuclphysa.2009.09.055}, abstractNote={Fermi gases with magnetically tunable interactions provide a clean and controllable laboratory system for modeling interparticle interactions between fermions in nature. The s-wave scattering length, which is dominant a low temperature, is made to diverge by tuning near a collisional (Feshbach) resonance. In this regime, two-component Fermi gases are stable and strongly interacting, enabling tests of nonperturbative many-body theories in a variety of disciplines, from high temperature superconductors to neutron matter and quark-gluon plasmas. We have developed model-independent methods for measuring the entropy and energy of this model system, providing a benchmark for calculations of the thermodynamics. Our experiments on the expansion of rotating strongly interacting Fermi gases in the normal fluid regime reveal extremely low viscosity hydrodynamics. Combining the thermodynamic and hydrodynamic measurements enables an estimate of the ratio of the shear viscosity to the entropy density. A strongly interacting Fermi gas in the normal fluid regime is found to be a nearly perfect fluid, where the ratio of the viscosity to the entropy density is close to a universal minimum that has been conjectured by string theory methods.}, number={1-4}, journal={Nuclear Physics A}, publisher={Elsevier BV}, author={Thomas, J.E.}, year={2009}, month={Nov}, pages={665c–672c} }
 @article{luo_thomas_2009, title={Thermodynamic Measurements in a Strongly Interacting Fermi Gas}, volume={154}, ISSN={0022-2291 1573-7357}, url={http://dx.doi.org/10.1007/s10909-008-9850-2}, DOI={10.1007/s10909-008-9850-2}, abstractNote={Strongly interacting Fermi gases provide a clean and controllable laboratory system for modeling strong interparticle interactions between fermions in nature, from high temperature superconductors to neutron matter and quark-gluon plasmas. Model-independent thermodynamic measurements, which do not require theoretical models for calibrations, are very important for exploring this important system experimentally, as they enable direct tests of predictions based on the best current non-perturbative many-body theories. At Duke University, we use all-optical methods to produce a strongly interacting Fermi gas of spin-1/2-up and spin-1/2-down 6Li atoms that is magnetically tuned near a collisional (Feshbach) resonance. We conduct a series of measurements on the thermodynamic properties of this unique quantum gas, including the energy E, entropy S, and sound velocity c. Our model-independent measurements of E and S enable a precision study of the finite temperature thermodynamics. The E(S) data are directly compared to several recent predictions. The temperature in both the superfluid and normal fluid regime is obtained from the fundamental thermodynamic relation T=∂ E/∂ S by parameterizing the E(S) data using two different power laws that are joined with continuous E and T at a certain entropy S c, where the fit is optimized. We observe a significant change in the scaling of E with S above and below S c. Taking the fitted value of S c as an estimate of the critical entropy for a superfluid-normal fluid phase transition in the strongly interacting Fermi gas, we estimate the critical parameters. Our E(S) data are also used to experimentally calibrate the endpoint temperatures obtained for adiabatic sweeps of the magnetic field between the ideal and strongly interacting regimes. This enables the first experimental calibration of the temperature scale used in experiments on fermionic pair condensation, where the ideal Fermi gas temperature is measured before sweeping the magnetic field to the strongly interacting regime. Our calibration shows that the ideal gas temperature measured for the onset of pair condensation corresponds closely to the critical temperature T c estimated in the strongly interacting regime from the fits to our E(S) data. We also calibrate the empirical temperature employed in studies of the heat capacity and obtain nearly the same T c. We determine the ground state energy by three different methods, using sound velocity measurements, by extrapolating E(S) to S=0 and by measuring the ratio of the cloud sizes in the strongly and weakly interacting regimes. The results are in very good agreement with recent predictions. Finally, using universal thermodynamic relations, we estimate the chemical potential and heat capacity of the trapped gas from the E(S) data.}, number={1-2}, journal={Journal of Low Temperature Physics}, publisher={Springer Science and Business Media LLC}, author={Luo, Le and Thomas, J. E.}, year={2009}, pages={1–29} }
 @article{turlapov_kinast_clancy_luo_joseph_thomas_2008, title={Is a Gas of Strongly Interacting Atomic Fermions a Nearly Perfect Fluid?}, volume={150}, ISSN={0022-2291 1573-7357}, url={http://dx.doi.org/10.1007/s10909-007-9589-1}, DOI={10.1007/s10909-007-9589-1}, abstractNote={We use all-optical methods to produce a highly-degenerate Fermi gas of spin-1/2 6Li atoms. A magnetic field tunes the gas near a collisional (Feshbach) resonance, producing strong interactions between spin-up and spin-down atoms. We have measured properties of a breathing mode over a wide range of temperatures. As the temperature is increased from below the superfluid transition to above, the frequency of the mode is always close to the hydrodynamic value, while the damping rate increases. A complete explanation of both the frequency and the damping rate in the normal collisional regime has not been achieved. Our measurements of the damping rate as a function of the energy of the gas are used to estimate an upper bound on the viscosity. Using our new measurements of the entropy of the gas, we estimate the ratio of the shear viscosity to the entropy density and compare the result with a recent string theory conjecture for the minimum viscosity of a perfect quantum fluid.}, number={3-4}, journal={Journal of Low Temperature Physics}, publisher={Springer Science and Business Media LLC}, author={Turlapov, A. and Kinast, J. and Clancy, B. and Luo, Le and Joseph, J. and Thomas, J. E.}, year={2008}, pages={567–576} }
 @article{thomas_2006, title={Superfluidity in the picture}, volume={442}, ISSN={0028-0836 1476-4687}, url={http://dx.doi.org/10.1038/442032a}, DOI={10.1038/442032a}, number={7098}, journal={Nature}, publisher={Springer Science and Business Media LLC}, author={Thomas, J. E.}, year={2006}, month={Jul}, pages={32–33} }
 @article{thomas_2006, title={Ultracold Fermi gas on a chip}, volume={2}, ISSN={1745-2473 1745-2481}, url={http://dx.doi.org/10.1038/nphys326}, DOI={10.1038/nphys326}, number={6}, journal={Nature Physics}, publisher={Springer Science and Business Media LLC}, author={Thomas, John E.}, year={2006}, month={Jun}, pages={377–378} }
 @article{kinast_turlapov_thomas_chen_stajic_levin_2005, title={Heat Capacity of a Strongly Interacting Fermi Gas}, volume={307}, ISSN={0036-8075 1095-9203}, url={http://dx.doi.org/10.1126/science.1109220}, DOI={10.1126/science.1109220}, abstractNote={We have measured the heat capacity of an optically trapped, strongly interacting Fermi gas of atoms. A precise addition of energy to the gas is followed by single-parameter thermometry, which determines the empirical temperature parameter of the gas cloud. Our measurements reveal a clear transition in the heat capacity. The energy and the spatial profile of the gas are computed using a theory of the crossover from Fermi to Bose superfluids at finite temperatures. The theory calibrates the empirical temperature parameter, yields excellent agreement with the data, and predicts the onset of superfluidity at the observed transition point.}, number={5713}, journal={Science}, publisher={American Association for the Advancement of Science (AAAS)}, author={Kinast, J. and Turlapov, A. and Thomas, J.E. and Chen, Q. and Stajic, J. and Levin, K.}, year={2005}, month={Feb}, pages={1296–1299} }
 @article{thomas_kinast_turlapov_2005, title={Virial Theorem and Universality in a Unitary Fermi Gas}, volume={95}, ISSN={0031-9007 1079-7114}, url={http://dx.doi.org/10.1103/physrevlett.95.120402}, DOI={10.1103/physrevlett.95.120402}, abstractNote={Unitary Fermi gases, where the scattering length is large compared to the interparticle spacing, can have universal properties, which are independent of the details of the interparticle interactions when the range of the scattering potential is negligible. We prepare an optically trapped, unitary Fermi gas of 6Li, tuned just above the center of a broad Feshbach resonance. In agreement with the universal hypothesis, we observe that this strongly interacting many-body system obeys the virial theorem for an ideal gas over a wide range of temperatures. Based on this result, we suggest a simple volume thermometry method for unitary gases. We also show that the observed breathing mode frequency, which is close to the unitary hydrodynamic value over a wide range of temperature, is consistent with a universal hydrodynamic gas with nearly isentropic dynamics.}, number={12}, journal={Physical Review Letters}, publisher={American Physical Society (APS)}, author={Thomas, J. E. and Kinast, J. and Turlapov, A.}, year={2005}, month={Sep} }
 @article{thomas_hemmer_kinast_turlapov_gehm_o'hara_2004, title={Dynamics of a Highly-Degenerate, Strongly-Interacting Fermi Gas of Atoms}, volume={134}, ISSN={0022-2291}, url={http://dx.doi.org/10.1023/b:jolt.0000012624.69815.77}, DOI={10.1023/b:jolt.0000012624.69815.77}, number={1/2}, journal={Journal of Low Temperature Physics}, publisher={Springer Science and Business Media LLC}, author={Thomas, J. E. and Hemmer, S. L. and Kinast, J. and Turlapov, A. and Gehm, M. E. and O'Hara, K. M.}, year={2004}, month={Jan}, pages={655–664} }
 @article{kinast_hemmer_gehm_turlapov_thomas_2004, title={Evidence for Superfluidity in a Resonantly Interacting Fermi Gas}, volume={92}, ISSN={0031-9007 1079-7114}, url={http://dx.doi.org/10.1103/physrevlett.92.150402}, DOI={10.1103/physrevlett.92.150402}, abstractNote={We observe collective oscillations of a trapped, degenerate Fermi gas of 6Li atoms at a magnetic field just above a Feshbach resonance, where the two-body physics does not support a bound state. The gas exhibits a radial breathing mode at a frequency of 2837(05) Hz, in excellent agreement with the frequency of nu(H) identical with sqrt[10nu(x)nu(y)/3]=2830(20) Hz predicted for a hydrodynamic Fermi gas with unitarity-limited interactions. The measured damping times and frequencies are inconsistent with predictions for both the collisionless mean field regime and for collisional hydrodynamics. These observations provide the first evidence for superfluid hydrodynamics in a resonantly interacting Fermi gas.}, number={15}, journal={Physical Review Letters}, publisher={American Physical Society (APS)}, author={Kinast, J. and Hemmer, S. L. and Gehm, M. E. and Turlapov, A. and Thomas, J. E.}, year={2004}, month={Apr} }
 @article{granade_gehm_o'hara_thomas_2002, title={All-Optical Production of a Degenerate Fermi Gas}, volume={88}, ISSN={0031-9007 1079-7114}, url={http://dx.doi.org/10.1103/physrevlett.88.120405}, DOI={10.1103/physrevlett.88.120405}, abstractNote={We achieve degeneracy in a mixture of the two lowest hyperfine states of 6Li by direct evaporation in a CO2 laser trap, yielding the first all optically produced degenerate Fermi gas. More than 10(5) atoms are confined at temperatures below 4 microK at full trap depth, where the Fermi temperature for each state is 8 microK. This degenerate two-component mixture is ideal for exploring mechanisms of superconductivity ranging from Cooper pairing to Bose-Einstein condensation of strongly bound pairs.}, number={12}, journal={Physical Review Letters}, publisher={American Physical Society (APS)}, author={Granade, S. R. and Gehm, M. E. and O'Hara, K. M. and Thomas, J. E.}, year={2002}, month={Mar} }
 @article{lee_thomas_2002, title={Experimental Simulation of Two-Particle Quantum Entanglement using Classical Fields}, volume={88}, ISSN={0031-9007 1079-7114}, url={http://dx.doi.org/10.1103/physrevlett.88.097902}, DOI={10.1103/physrevlett.88.097902}, abstractNote={We experimentally demonstrate simulation of two entangled quantum bits using classical fields of two frequencies and two polarizations. Multiplication of optical heterodyne beat signals from two spatially separated regions simulates coincidence detection of two particles. The product signal so obtained contains several frequency components, one of which can be selected by bandpass frequency filtering. The bandpassed signal contains two indistinguishable, interfering contributions, permitting simulation of four polarization-entangled Bell-like states. These classical field methods may be useful in small scale simulations of quantum logic operations that require multiparticle entanglement without collapse.}, number={9}, journal={Physical Review Letters}, publisher={American Physical Society (APS)}, author={Lee, K. F. and Thomas, J. E.}, year={2002}, month={Feb} }
 @article{o’hara_hemmer_gehm_granade_thomas_2002, title={Observation of a Strongly Interacting Degenerate Fermi Gas of Atoms}, volume={298}, ISSN={0036-8075 1095-9203}, url={http://dx.doi.org/10.1126/science.1079107}, DOI={10.1126/science.1079107}, abstractNote={We report on the observation of a highly degenerate, strongly interacting Fermi gas of atoms. Fermionic lithium-6 atoms in an optical trap are evaporatively cooled to degeneracy using a magnetic field to induce strong, resonant interactions. Upon abruptly releasing the cloud from the trap, the gas is observed to expand rapidly in the transverse direction while remaining nearly stationary in the axial direction. We interpret the expansion dynamics in terms of collisionless superfluid and collisional hydrodynamics. For the data taken at the longest evaporation times, we find that collisional hydrodynamics does not provide a satisfactory explanation, whereas superfluidity is plausible.}, number={5601}, journal={Science}, publisher={American Association for the Advancement of Science (AAAS)}, author={O’Hara, K.M. and Hemmer, S.L. and Gehm, M.E. and Granade, S.R. and Thomas, J.E.}, year={2002}, month={Nov}, pages={2179–2182} }
 @article{o’hara_gehm_granade_thomas_2001, title={Scaling laws for evaporative cooling in time-dependent optical traps}, volume={64}, ISSN={1050-2947 1094-1622}, url={http://dx.doi.org/10.1103/physreva.64.051403}, DOI={10.1103/physreva.64.051403}, abstractNote={We derive scaling laws for the number of atoms, collision rate, and phase-space density as a function of trap depth for evaporative cooling in an adiabadically lowered optical trap. The results are in excellent agreement with a Boltzmann equation model and show that very large increases in phase-space density can be obtained without excessive slowing of the evaporation rate. Predictions are in reasonable agreement with a recent experiment that achieves Bose-Einstein condensation by evaporation in an optical trap. We also discuss evaporation of fermionic mixtures and explain why Pauli blocking does not strongly inhibit cooling.}, number={5}, journal={Physical Review A}, publisher={American Physical Society (APS)}, author={O’Hara, K. M. and Gehm, M. E. and Granade, S. R. and Thomas, J. E.}, year={2001}, month={Oct} }
 @article{savard_o’hara_thomas_1997, title={Laser-noise-induced heating in far-off resonance optical traps}, volume={56}, ISSN={1050-2947 1094-1622}, url={http://dx.doi.org/10.1103/physreva.56.r1095}, DOI={10.1103/physreva.56.r1095}, abstractNote={We calculate the heating rates arising from laser intensity noise and beam pointing fluctuations in far off resonance optical traps. Achievement of long heating time constants imposes stringent requirements on the laser noise spectra.}, number={2}, journal={Physical Review A}, publisher={American Physical Society (APS)}, author={Savard, T. A. and O’Hara, K. M. and Thomas, J. E.}, year={1997}, month={Aug}, pages={R1095–R1098} }
 @article{gardner_marable_welch_thomas_1993, title={Suboptical wavelength position measurement of moving atoms using optical fields}, volume={70}, ISSN={0031-9007}, url={http://dx.doi.org/10.1103/physrevlett.70.3404}, DOI={10.1103/physrevlett.70.3404}, abstractNote={We demonstrate all-optical techniques for position measurement and localization of moving atoms with suboptical wavelength precision. Spatial resolution of 200 nanometers, with linearity over a few microns, is obtained by the methods which ultimately will scale to yield nanometer resolution limited by the uncertainty principle}, number={22}, journal={Physical Review Letters}, publisher={American Physical Society (APS)}, author={Gardner, J. R. and Marable, M. L. and Welch, G. R. and Thomas, J. E.}, year={1993}, month={May}, pages={3404–3407} }